Tackifier resins are commonly made by polymerizing 2-methyl-2-butene and piperylene with additional unsaturated hydrocarbons that contain from about 4 to about 18 carbon atoms. Such tackifier resins are widely utilized in manufacturing pressure sensitive and hot melt adhesives. Pressure sensitive adhesives are used in tapes, labels, adhesive bandages, glue traps for rats and mice, and numerous additional applications. Hot melt adhesives are employed in carton closures, book bindings, film lamination, tires, labels, tapes, packaging, and a wide variety of other products.
Tackifier resins based on hydrocarbon monomers that contain 5 carbon atoms (C5 hydrocarbons) offer unique characteristics that allow them to be used in applications where most other hydrocarbon resins do not adequately perform. Their light color, high tack properties, low specific gravity, oxidative stability and day-to-day consistency of properties make them an excellent choice for use in pressure sensitive adhesives. Pressure sensitive adhesives of this type are normally made by blending the C5 hydrocarbon tackifier resin with a rubbery polymer, such as natural rubber, butadiene-styrene copolymers, butadiene-acrylonitrile copolymers, or a stereo specific polymer of a diene monomer, such as butadiene or isoprene. U.S. Pat. No. 3,846,352 describes pressure sensitive adhesive compositions of this type.
U.S. Pat. No. 4,060,503 discloses a rubber, xcex1-methylstyrene-modified piperylene/2-methyl-2-butene resin adhesive composition which comprises an admixture of (1) about 100 parts by weight of a rubber comprised of at least one of natural rubber, synthetic cis-1,4-polyisoprene elastomer, and an unvulcanized elastomeric styrene/isoprene block copolymer having the general configuration A-B-A wherein each A is an independently selected nonelastomeric styrene polymer block having an average molecular weight of about 2,000 to about 100,000 and a glass transition temperature above about 25xc2x0 C., the total block A content being from about 10 to about 50 percent by weight of the copolymer, and B is an elastomeric conjugated diene block of polyisoprene having an average molecular weight from about 25,000 to about 1,000,000 and a glass transition temperature below about 10xc2x0 C., said copolymer having a tensile strength at 25xc2x0 C. in excess of about 200 pounds per square inch, and (2) about 60 to about 140 parts by weight of a compatible piperylene/2-methyl-2-butene type, thermoplastic tackifying resin, modified with a minor amount of xcex1-methylstyrene containing carbon-to-carbon unsaturation therein and having a softening point in the range of about 80xc2x0 C. to about 105xc2x0 C. prepared by the method which comprises reacting in the presence of an aliphatic hydrocarbon solvent and a catalyst selected from at least one of aluminum chloride and ethylaluminum dichloride, a monomer mixture consisting of about 92 to about 99 weight percent of a diolefin/olefin mixture of a weight ratio in the range of about 0.6/1 to about 1.4/1 and, correspondingly, about 8 to about 1 weight percent xcex1-methylstyrene, where said diolefin is at least about 95 weight percent piperylene and said olefin is 2-methyl-2-butene; wherein said diolefin is optionally modified by containing up to about 5 weight percent isoprene and wherein said monomer mixture is optionally modified by containing up to about 10 weight percent of at least one monomer selected from the group consisting of piperylene dimers, piperylene trimers, 2-methyl-1-butene, 2-methyl-2-pentene, 2-methyl-1-pentene, 2,3-dimethyl-1-butene, 2,3-dimethyl-2-butene, 2-methyl-2-pentene, cyclopentene and 1,3-cyclopentadiene.
U.S. Pat. No. 4,288,567 discloses an adhesive composition which comprises an admixture of an unvulcanized block polymer product and a compatible tackifier resin therefor prepared by the method which comprises (A) mixing (1) 100 parts by weight of a solution polymerizate comprised of 100 parts by weight of an unvulcanized block styrene/isoprene polymer product with an overall styrene polymer content in the range of about 10 to 35 weight percent and its polymerization solvent in the range of about 300 to about 1100 parts by weight with (2) about 50 to about 200 parts by weight of a solution polymerizate comprised of 100 parts by weight of a tackifying resin for said block polymer product and its polymerization solvent in the range of about 25 to about 1100 parts by weight and (B) removing said solvent from the prepared mixture prior to its application as an adhesive; wherein the total of said polymerization solvents is a solvent for the combination of said block polymer and said resin; wherein said block polymer polymerizate is produced by the process of contacting isoprene and a suitable amount of divinylbenzene under solution polymerization conditions with a polystyryllithium catalyst, said amount of divinylbenzene being from about 0.5/1 to about 10/1 moles of divinylbenzene per mole of active lithium catalyst; and wherein said tackifier resin polymerizate is prepared by copolymerizing in the presence of a catalyst selected from the group consisting of aluminum chloride, boron trifluoride and boron trifluoride etherate, a mixture of piperylene and at least one olefin containing 4-6 carbon atoms in a diolefin/olefin mole ratio in the range of about 0.6/1 to about 2.5/1, optionally modified by copolymerizing about 5 to about 20 weight percent, based on the total monomers, of at least one additional monomer selected from alpha-methylstyrene and di-cyclopentadiene in which the resin itself has a softening point in the range of about 50xc2x0 C. to about 150xc2x0 C.
U.S. Pat. No. 4,172,860 discloses an adhesive composition comprises an admixture of (A) 100 parts by weight of an unvulcanized branched, thermoplastic block polymer product produced by the process consisting essentially of contacting a diolefin selected from the group consisting of at least one of isoprene and 1,3-butadiene premixed with a suitable amount of divinylbenzene, under solution polymerization conditions with a polystyryl lithium catalyst, said amount of divinylbenzene being from about 0.5/1 to about 10/1 moles of divinylbenzene per mole of active lithium catalyst to form said thermoplastic block polymer that is essentially non-gel and has the divinylbenzene coupling agent attached to the diolefinic portion of the block polymer, and (B) about 50 to about 150 parts by weight tackifier therefor; where said tackifier is a resin having a softening point in the range of about 50xc2x0 C. to about 150xc2x0 C. and is selected from at least one of terpene resins and synthetic hydrocarbon resins derived essentially as diolefin/olefin copolymers prepared by polymerizing the monomers in the presence of a catalyst selected from aluminum chloride or boron trifluoride or boron trifluoride etherate; and where, in said block copolymer, the polystyrene block molecular weight is in the range of about 8,000 to about 45,000, the polydiolefin block has a molecular weight in the range of about 10,000 to about 100,000, ignoring the divinylbenzene effect, with the overall styrene content in the block copolymer being in the range of 10 to 35 weight percent.
U.S. Pat. No. 3,577,398 is based upon the finding that a mixture of piperylene and 2-methyl-2-butene can be polymerized in the presence of a metal halide catalyst, such as aluminum chloride or stannic chloride, to form a tackifier resin that is useful in commercial applications. U.S. Pat. No. 3,577,398 specifically discloses a polymeric resinous composition comprising from about 40 to about 80 weight percent units derived from piperylene and from about 20 to about 60 weight percent units derived from 2-methyl-2-butene, wherein the resinous composition has a softening point that is within the range of about 80xc2x0 C. to about 110xc2x0 C. U.S. Pat. No. 3,577,398 indicates that the polymeric resinous composition can be modified by having up to about 25 weight percent units derived from certain other unsaturated hydrocarbons. The polymeric resinous composition is prepared by polymerizing a mixture comprising from about 20 to about 75 weight percent piperylene and from about 25 to about 80 weight percent of 2-methyl-2-butene in the presence of an anhydrous metal halide selected from aluminum chloride and stannic chloride.
U.S. Pat. Nos. 3,784,530 and 3,846,353 disclose a resinous material that is particularly useful as a tackifier for rubbery butadiene-styrene copolymers that has a softening point in the range of 60xc2x0 C. to about 110xc2x0 C. that is prepared by polymerizing piperylene, 2-methyl-2-butene, dicyclopentadiene, and xcex1-methylstyrene in the presence of a catalyst selected from the group consisting of aluminum chloride and ethyl aluminum dichloride and a solvent selected from aliphatic and aromatic hydrocarbons.
This invention is based upon the unexpected discovery that the reactivity of the most important monomers commonly used in synthesizing tackifier resins with aluminum halide catalysts can be enhanced by conducting the polymerization in the presence of an allylic halide. For instance, the conversions of 2-methyl-2-butene, cis-piperylene, and cyclopentene that are attained in polymerizations that are catalyzed with aluminum halide catalysts are increased by conducting the polymerization in the presence of an allylic halide, such as allyl chloride. Increased conversion is of great commercial importance because it leads to reduced cost that is attributable an increased level of efficiency and reactor capacity. The increased conversion of expensive monomers used in making the tackifier resin is of particular benefit. The implementation of this invention also reaps significant environmental benefits in that a greater level of monomers are consumed by the polymerization reaction and accordingly less unreacted monomers have to be disposed of.
The present invention more specifically discloses a process for synthesizing a resin having characteristics that make it particularly useful as a tackifier resin, said process comprising the polymerization of an unsaturated hydrocarbon monomer mixture in the presence of aluminum halide and an allylic halide, wherein the unsaturated hydrocarbon monomer mixture is comprised of unsaturated hyrdocarbon monomers containing from about 4 to about 18 carbon atoms.
The subject invention further reveals a process for synthesizing a resin having characteristics that make it particularly useful as a tackifier resin, said process comprising the polymerization of an unsaturated hydrocarbon monomer mixture in the presence of aluminum halide and an allylic halide, wherein the unsaturated hydrocarbon monomer mixture is comprised of 2-methyl-2-butene, cis-piperylene, trans-piperylene, cyclopentene, and additional unsaturated hyrdocarbon monomers containing from about 4 to about 18 carbon atoms.
In the process of polymerizing an unsaturated hydrocarbon monomer utilizing an aluminum halide catalyst, the present invention generally discloses the improvement which comprises conducting the polymerization in the presence of an allylic halide.
The subject invention can be practiced by conducting polymerizations that are catalyzed with aluminum halide in the presence of an allylic halide to enhance the level of monomer conversion. The allylic halides that can be used in the practice of this invention are of the structural formula: 
wherein X represents a halogen atom, wherein R1 and R2 can be the same or different, and wherein R1 and R2 represent alkyl groups containing from 1 to about 8 carbon atoms or hydrogen atoms. The halogen in the allylic halide will typically be chlorine or bromine. In most cases the halogen in the allylic halide will be chlorine. R1 and R2 will normally represent a hydrogen atom or an alkyl group containing from 1 to about 4 carbon atoms, such as a methyl group. R2 will normally represent a hydrogen atom.
This invention is generally applicable to any polymerization of an unsaturated hydrocarbon monomer that is catalyzed with aluminum halide, such as aluminum chloride (AlCl3). However, it is of particular utility in the polymerization of mixtures of unsaturated hydrocarbon monomers containing from about 4 to about 18 carbon atoms. For instance, the conversion attained in the polymerization of unsaturated hydrocarbon monomer mixtures with aluminum halide catalysts into tackifier resins can be increased using the technique of this invention. The unsaturated hydrocarbon monomers in such mixtures will typically contain from about 5 to about 8 carbon atoms. The unsaturated hydrocarbon monomers in such mixtures will more typically contain about 5 carbon atoms. The mixture of unsaturated hydrocarbon monomers will frequently contain a substantial amount of 2-methyl-2-butene, cis-piperylene, trans-piperylene, and cyclopentene. In many cases tackifier resins will be made by utilizing a mixture of unsaturated hydrocarbon monomers that contain a total of over 50 weight percent 2-methyl-2-butene, cis-piperylene, trans-piperylene, and cyclopentene as constituents of the mixture. Such unsaturated hydrocarbon monomer mixtures, of course, also include additional unsaturated hydrocarbon monomers. Some common representative examples of additional unsaturated hydrocarbons that can be used include isobutylene, 2-methyl-1-butene, 2,3-dimethyl-1-butene, 2,3-dimethyl-2-butene, 3,3-dimethyl-1-butene, 1-pentene, 2-pentene, 2-methyl-1-pentene, 2-methyl-2-pentene, 3-methyl-2-pentene, 4-methyl-1-pentene, 4-methyl-2-pentene, 2-hexene, isoprene, cyclohexene, 1-octene, 2-octene, 2-dodecene, 2-octadecene, 2-methyl-1-heptadecene, and 1,3-cyclopentadiene.
The polymerizations of this invention are carried out using the general techniques disclosed in U.S. Pat. Nos. 3,577,398, 3,784,530, 3,872,064, 4,038,346, and 4,230,842 with the polymerization, of course, being conducted in the presence of an allylic halide. The teachings of U.S. Pat. Nos. 3,577,398, 3,784,530, 3,872,064, 4,038,346, and 4,230,842 are accordingly incorporated herein by reference in their entirety.
The aluminum halide will typically be aluminum chloride and will normally be used in an amount which is within the range of about 0.05 phm (parts per 100 parts by weight of monomer) to about 10 phm. The aluminum halide will more typically be used in an amount that is within the range of about 0.5 phm to about 5 phm, and will normally be used in an amount within the range of about 1 phr to about 3 phm. The aluminum halide will preferably be used at a level of about 2 phm. The aluminum halide will typically be employed as anhydrous particles having a particle size that is within the range of about 5 to about 200 mesh. However, it should be noted that larger or smaller particles of the aluminum halide can be used.
The weight ratio of the aluminum halide to the allylic halide will typically be within the range of about 1:4 to about 50:1. The weight ratio of the aluminum halide to the allylic halide will more typically be within the range of about 1:1 to about 20:1. The weight ratio of the aluminum halide to the allylic halide will preferable be within the range of about 2:1 to about 8:1. The weight ratio of the aluminum halide to the allylic halide will more preferably be about 7:1.
The polymerization reactions of this invention are typically carried out in the presence of a diluent because they are usually exothermic. However, with adequate mixing and cooling the reaction temperature can be controlled and the reaction can accordingly be conducted without the need for a diluent being present. In any case, various liquid organic diluents can be employed in the polymerization. Some representative examples of organic solvents that can be used as diluents include, aliphatic hydrocarbons, such as pentanes, hexanes, and heptanes, and aromatic hydrocarbons, such as benzene, xylene, and toluene. Unreacted residual hydrocarbons from the polymerization reaction can also be allowed to remain in the polymerization mixture and a diluent.
The monomers, organic solvent, aluminum halide, and allylic halide can be added to a polymerization reactor simultaneously or intermittently. The reaction can be conducted continuously, semi-continuously, or by utilizing batch polymerization techniques. In the preparation of tackifier resins, a wide range of temperatures are suitable for the polymerization. For example, the polymerization can be carried out at a temperature that is in the range of about xe2x88x9220xc2x0 C. to about 100xc2x0 C. The polymerization is typically conducted at a temperature that is within the range of about 0xc2x0 C. to about 50xc2x0 C. The polymerization is more typically conducted at a temperature that is within the range of about 10xc2x0 C. to about 45xc2x0 C. The polymerization is preferably conducted at a temperature that is within the range of about 25xc2x0 C. to about 40xc2x0 C. However, a temperature will normally be above the freezing point of the reaction system and below its boiling point. Accordingly, the pressure at which the polymerization reaction is being conducted should be taken into consideration when determining the optimum temperature. Normally, the polymerization reaction pressures may be atmospheric or above or below atmospheric pressure. Generally, a satisfactory polymerization is conducted at about autogenous pressure developed under the operating conditions used.
The prepared thermoplastic tackifying resin polymer is conveniently recovered by steam distillation or vacuum distillation to remove volatile unreacted monomers, dimers, trimers, low molecular weight oily polymers, and the like. The thermoplastic tackifying resins will normally have a softening point that is within the range of about 50xc2x0 C. to about 175xc2x0 C. as determined by ASTM Method E28-58T and more preferably from about 80xc2x0 C. to about 130xc2x0 C. Such tackifier resins also typically have a specific gravity at 25xc2x0 C. that is within the range of about 0.93 to about 0.99, a glass transition temperature (onset) that is within the range of about 30xc2x0 C. to 80xc2x0 C., and are light in color. They are typically derived from aliphatic and alicyclic hydrocarbons, preferably aliphatic hydrocarbons, and therefore contain essentially no units derived from aromatic hydrocarbons. In this regard, it is sometimes preferred that not more than about 5 percent by weight of the units of the tackifying resin are derived from aromatic hydrocarbons and more preferably it is desired that none of the units are derived from aromatic hydrocarbons. In other cases it is desirable to include a vinyl aromatic monomer, such as styrene or xcex1-methyl styrene, in the resin to attain desired characteristics as described in U.S. Pat. No. 4,230,842. Furthermore, it is preferred for the tackifying resin to contain carbon-to-carbon unsaturation therein. Therefore, it is preferred that at least a portion of the hydrocarbons used to prepare the resin have at least two carbon-to-carbon double bonds therein.
The tackifier resins made by the technique of this invention can be utilized in manufacturing pressure sensitive and hot melt adhesives. Pressure sensitive adhesives that can be manufactured with such tackifier resins include those used in tapes (including those used to close diapers), labels, adhesive bandages, glue traps for insects and rodents, including rats and mice, fly paper and numerous additional applications. Hot melt adhesives that can be manufactured using tackifier resins made by the process of this invention can be employed in carton closures, book bindings, film lamination, labels, tapes, packaging, product assembly (including in non-woven fabric applications including diapers) and a wide variety of other products. Such adhesives are typically made by blending the tackifier resin with a rubbery polymer, such as natural rubber, butadiene-styrene copolymers, butadiene-acrylonitrile copolymers, or a stereo specific polymer of a diene monomer, such as butadiene or isoprene. U.S. Pat. No. 3,846,352 describes pressure sensitive adhesive compositions of this type. The teachings of U.S. Pat. No. 3,846,352 are incorporated herein by reference in their entirety.
This invention is illustrated by the following examples that are merely for the purpose of illustration and are not to be regarded as limiting the scope of the invention or the manner in which it can be practiced. Unless specifically indicated otherwise, parts and percentages are given by weight.